Systems and methods related to the treatment of back pain

ABSTRACT

The present invention reduces pain and improves function long-term in persons with back pain using electrical stimulation in the back. This approach involves an electrical stimulation device including at least one electrode adapted for insertion within an animal body with back pain and at least one pulse generator operatively coupled with the at least one electrode, wherein the pulse generator delivers electrical stimulation activating at least one muscle in a back of the animal body for pain relief.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/843,002, entitled “Systems and Methods Related to the Treatment ofBack Pain,” filed on Mar. 15, 2013, which claims the benefit from U.S.Provisional Patent Application Ser. No. 61/611,560 entitled “Systems andMethods Related to the Treatment of Back Pain” filed on Mar. 15, 2012,which are both hereby incorporated in their entirety by reference.

FIELD OF INVENTION

The present invention generally relates to a system and a method todeliver percutaneous stimulation to relieve pain and improve function inpatients with back pain.

BACKGROUND OF THE INVENTION

Back pain (e.g., low back pain (LBP) lasting approximately 12 weeks)affects approximately tens of millions of people in the U.S. and is thesecond leading cause of disability (6.8 million people). Back pain isassociated with reduced activities of daily living (e.g., walking,housework, personal care) and health-related quality of life. Inaddition, back pain is expensive to treat and often leads to missed workdays (149 million days/year) and reduced productivity, resulting intotal costs of $100-200 billion/year in the U.S.

Present methods to relieve back pain are ineffective, expensive,inconvenient, and/or invasive. For example, oral medications (e.g.,acetaminophen, NSAIDs, muscle relaxants, tricyclic antidepressants,antiepileptics, and corticosteroids) provide only limited and/orshort-lived pain relief, and typically produce side effects (e.g.,sedation, dizziness, and gastrointestinal problems). Although opioidscan provide substantial short-term pain relief, they are not recommendedas a treatment to control chronic back pain, since long-term use canresult in dependence and severe side effects.

Exercise (including yoga, stretching, strength training) has a low levelof risk and can relieve pain and improve function long-term, butpatients often fail to comply with treatment regimens due to discomfort,lack of motivation, and inconvenience.

Physical manipulation (i.e., massage, spinal manipulation) has a lowlevel of risk and can provide short-term pain relief. However, evidencefor the long-term benefit of physical manipulation has been mixed.Further, frequent treatment sessions are required to maintain painrelief, which is inconvenient for patients.

Acupuncture is minimally-invasive, and studies have suggested thatacupuncture can provide pain relief. However, study design inacupuncture studies has been questionable (e.g., adequacy ofsham/placebo/control), and the effectiveness of acupuncture remainscontroversial.

Injections of steroids or anesthetic provide short-term pain relief butseldom produce long-term benefit. As well, injections of such medicinesproduce side effects, including increased pain, lightheadedness,headache, infection, and nausea and vomiting.

Intrathecal drug therapy can be effective for reducing pain but requiresan invasive procedure and is limited by a host of frequent side effects(e.g., nausea, infection, intrathecal granuloma). Also, technicalcomplications (i.e., problems with catheter or pump) are common and mayrequire reoperation or removal of the device.

Surgical procedures for back pain (e.g., spinal fusion, discreplacement) are highly invasive, irreversible, carry risks ofcomplications, and reduce pain in less than half of patients. Also,surgeries for chronic back pain frequently require reoperation.

Existing methods of electrical stimulation reduce pain by generatingparenthesis (i.e., tingling sensation) overlapping the regions of pain.Pain relief using these existing methods persists only for a short timefollowing treatment (e.g., hours to days), and this suggests thatchronic pain has not been reversed. As a result, only a small percentageof patients using existing methods of electrical stimulation experiencedclinically significant reductions in chronic axial low back painpost-treatment.

TENS is a non-invasive method to deliver electrical stimulation throughsurface electrodes to generate paresthesia coverage of the regions ofpain. TENS requires frequent treatment sessions to maintain pain relief,but consistent efficacy in chronic low back pain has not beendemonstrated. Although TENS can be self-administered at home, TENSsystems are cumbersome and not practical for daily use. Also, TENS canactivate cutaneous fibers and cause irritation and discomfort, limitingthe maximum tolerable stimulation intensity and treatment duration thatcan be delivered and reducing the potential efficacy of the treatment.

Spinal cord stimulation is a method to deliver electrical stimulationthrough implanted leads connected to an implanted pulse generator togenerate paresthesia coverage of the regions of pain. Spinal cordstimulation requires complex and invasive surgery to implant the leadsand pulse generator. Spinal cord stimulation has a moderate rate ofcomplications, including additional pain and hardware complications, andas a result, revision surgery, reprogramming, or removal of thestimulator is often required.

In summary, present treatments for back pain seldom provide adequatelong-term relief of pain or improvements in function; carry risks ofside effects and complications; and/or are invasive.

There remains room in the art of pain management for improved systemsand methods to be used to assist in the treatment of back pain.

SUMMARY OF THE INVENTION

Embodiments according to the present invention provide improved systemsand methods to be used to assist in the treatment of back pain.

The invention provides an electrical stimulation device having at leastone electrode adapted for insertion within an animal body with back painand at least one pulse generator operatively coupled with the at leastone electrode, wherein the pulse generator delivers electricalstimulation activating at least one muscle in a back of the animal bodyfor pain relief.

The invention also provides an electrical stimulation device having atleast one electrode adapted for insertion below skin of an animal bodywith back pain and a pulse generator operatively coupled with the atleast one electrode, wherein the pulse generator delivers electricalstimulation for a prescribed period of time to activate at least onemuscle in a back of the animal body to relive pain.

The invention further provides a method to alleviate back pain includingplacing at least one electrode within a tissue of an animal body, andapplying stimulation through the at least one electrode to activate atleast one muscle in a back of the animal body with back pain.

Other features and advantages of the inventions are set forth in thefollowing specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Operation of the invention may be better understood by reference to thedetailed description taken in connection with the followingillustrations, wherein:

FIG. 1 is a frontal view of a stimulation pulse train generator;

FIG. 2 is a top view of an electrode and percutaneous electrode lead;

FIG. 3 graphically illustrates the stimulation paradigm of apercutaneous stimulation system;

FIG. 4 is a cross-sectional view of the innervation of paraspinalmuscles;

FIG. 5 is two different side views of the insertion of a lead into ananimal body;

FIG. 6 is an example of a coordinate system to guide electrode placementbased on anatomical landmarks including the posterior superior iliacspine (PSIS);

FIGS. 7A-7J illustrate placement of the percutaneous lead(s) into themuscles of the back and the associated regions of muscle activation; and

FIG. 8 illustrates placement of the percutaneous leads and pulsegenerators on a patient's body.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. It is to be understood that other embodiments may be utilizedand structural and functional changes may be made without departing fromthe respective scope of the invention. Moreover, features of the variousembodiments may be combined or altered without departing from the scopeof the invention. As such, the following description is presented by wayof illustration only and should not limit in any way the variousalternatives and modifications that may be made to the illustratedembodiments and still be within the spirit and scope of the invention.

Any elements described herein as singular can be pluralized (i.e.,anything described as “one” can be more than one). Any species elementof a genus element can have the characteristics or elements of any otherspecies element of that genus. The described configurations, elements orcomplete assemblies and methods and their elements for carrying out theinvention, and variations of aspects of the invention can be combinedand modified with each other in any combination.

Although the disclosure hereof is detailed and exact to enable thoseskilled in the art to practice the invention, the physical embodimentsherein disclosed merely exemplify the invention which may be embodied inother specific structures. While the preferred embodiment has beendescribed, the details may be changed without departing from theinvention.

The stimulation system discussed below involves inserting an electrodeinto an animal body and using electrical stimulation to activate amuscle to provide pain relief. Any method of electrical stimulation willwork to activate the at least one muscle in the body.

With reference to FIG. 1 , a percutaneous stimulation system is shownthat can be used with the method of treating the back in accordance withthe present teachings. The stimulator may include an electricalstimulation pulse generator 10. The pulse generator 10 may include alightweight, durable housing 12 that may be fabricated from a suitableplastic or the like. In some embodiments, the case 12 may include a clipthat allows the pulse generator 10 to be releasably connected to apatient's belt, other clothing, or any other convenient location. Thecase 12 may also include a releasable battery access cover. Other meansof securing the stimulator may be used that allow the stimulator to besecured to the patient's skin without and/or under clothing (e.g.,adhesive, magnet, etc.).

For output of data to a patient or clinician operating the stimulationsystem, a visual display 20 may be provided. The display 20 may be by aliquid crystal display, but any other suitable display may alternativelybe used. An audio output device, such as a beeper may also be provided.Alternatively, data may be conveyed to the user in other ways (e.g.,tactile, flashing LEDs).

For user control, adjustment, and selection of operational parameters,the stimulation pulse generator 10 may include a mechanism or device forinput of data. The pulse generator 10 may include an increment switch24, a decrement switch 26, and a select or “enter” switch 28.

The increment and decrement switches 24, 26 may be used to cycle throughoperational modes or patterns and stimulation parameters displayed onthe display 20, while the select switch 28 may be used to select aparticular displayed operational pattern or stimulation parameter. Theselect switch 28 may also act as a power on/off toggle switch.

For output of electrical stimulation pulse train signals, the pulsetrain generator 10 may include an external connection socket (not shown)that may mate with a connector of an electrode cable assembly (notshown) to interconnect the pulse generator 10 with a plurality ofelectrodes, such as through use of percutaneous electrode leads. Moreparticularly the cable assembly connected to the socket 30 may include asecond connector such as on a distal end that may mate with a connectorattached to the proximal end of each of the percutaneous stimulationelectrode leads and a reference electrode lead. Alternatively, the pulsegenerator may transmit signals without a physical connection to theelectrode (e.g., radio-frequency coupling, passive polarization ofelectrode) or may be housed within a single unit along with theelectrode.

Exemplary embodiments of an electrode and percutaneous lead are shown inFIG. 2 . The electrode lead 40 may be fabricated from a 7-strandstainless steel wire insulated with a biocompatible polymer. Eachindividual wire strand may have a diameter of approximately 34 μm andthe insulated multi-strand lead wire may have a diameter ofapproximately 250 μm. It should be understood, however, that thesedimensions are merely exemplary and the present teachings are notlimited to such. Any appropriate sized, shaped and configured electrodeand percutaneous lead may be used. The insulated wire may be formed intoa spiral or helix as has been found to accommodate high dynamic stressupon muscle flexion and extension, while simultaneously retaining lowsusceptibility to fatigue. The outer diameter of the helically formedelectrode lead 40 may be approximately 580 μm and it may be encased orfilled with silicone or the like. Alternatively, the lead may haveadditional or fewer strands, may be made out of a different material(e.g., another metal, conducting polymer), may be insulated with anothermaterial, or may not be insulated. Further, the lead may be the sametype of use for spinal cord stimulation (e.g., cylindrical orpaddle-type leads).

As mentioned above, a proximal end 44 of each of the plurality ofelectrode lead wires 40 may be located exterior to the patient's bodywhen in use. The proximal end 44 may include a deinsulated length forconnection to an electrical connector in combination with the remainderof the electrode leads. The deinsulated portion may be located on anyportion of the proximal portion of the lead located outside of the body.In some embodiments, the distal end 46 of each lead 40, which may beinserted directly into tissue, may also include a deinsulated length.The deinsulated length may act as the stimulation electrode 50. At leasta portion of the deinsulated length may be bent or otherwise deformedinto a barb 48. This may anchor the electrode in the selected tissue. Ataper 52, made from silicone adhesive or the like, may be formed betweenthe deinsulated distal end 50 and the insulated portion of the lead 40to reduce stress concentration. The electrode may be placed anywherealong the length of the lead; the present teachings are not limited tothe aforementioned locations. The electrode may be a conductive contactconnected (e.g., welded, via adhesive) to the lead. Alternatively, thelead may be threaded (i.e., like a screw), and may be screwed into thetissue, which will mechanically secure the lead in the tissue.

Unlike surface electrodes that are applied to the surface of thepatient's skin using an adhesive, each of the plurality of percutaneouselectrodes 50 may be surgically implanted or otherwise inserted intoselect patient's tissue. The associated electrode lead 40 may exit thepatient percutaneously, i.e., through the skin, for connection to thestimulation pulse generator 10. Each of the electrodes 50 may beimplanted or otherwise inserted into the select tissues by use of aneedle. The needle may be straight or may be hooked. Alternatively, thelead may be inserted using other hollow tubes (e.g., cannula, catheter)or may be “shot” out of a device at sufficiently high speeds such that arigid structure (e.g., needle) is not needed to penetrate the skin.Alternatively, the lead may be introduced through a vessel (e.g., vein,artery). Alternatively, the lead itself may be rigid, enabling the leadto be insertable into the tissue without another object (e.g., aneedle). Alternatively, or in addition, tissues may be surgicallyexposed for implantation or minimally invasive techniques such asarthroscopy may be used. Alternatively, multiple electrodes may be on anarray (e.g., paddle electrode, cylindrical electrode, array of needles,etc.). Once all of the electrodes are implanted as desired, theirproximal ends may be crimped into a common connector that may mate withthe cable assembly. The cable assembly may be, in turn, connected to thepulse generator 10 through the connection socket 30. Alternatively, theelectrodes may be connected directly to the stimulator. Alternatively,each electrode may be connected to an individual connector. Alternativemeans of securing the leads to the connector may also be used (e.g.,magnetic, adhesive). Alternatively, the proximal ends of the leads mayterminate on a plug (e.g., banana plug, BNC plug) that can be connectedto the stimulator either directly or via a connector. Such therapies oruses may require multiple systems, which utilize multiple pulse traingenerators with multiple common connectors.

The present percutaneous stimulation system may allow for preciseselection of muscle stimulation and use of two or more stimulationelectrodes and channels. Alternatively, a system may use one stimulationelectrode. The system in accordance with the present invention may usetwo or more electrodes 50, each connected to an independent electrodestimulation channel E, and a single reference electrode 52 that may be apercutaneous, surface electrode, the case of the stimulator (ifimplanted), or an implanted electrode. Alternatively, there may be morethan one reference electrode, and each stimulation channel may have itsown reference electrode. The electrode stimulation channels may not beindependent, i.e., the same stimulation may be delivered to multiplechannels at once.

The stimulation pulse generator 10 may include a microprocessor-basedstimulation pulse generator circuit with a micro controller such as aMotorola 68HC12. Operational instructions or other information may bestored in non-volatile storage. Set stimulation therapy or patterns maybe included in this storage. These therapies may be based upongeneralized information such as may be gathered from radiographicevaluation in multiple dimensions along with selected stimulation.Ultimately patient specific information may be incorporated into thestimulation parameters in order to optimize the therapy for a particularindividual application. Preferably, the nonvolatile memory may alsoprovide storage for all patient-specific stimulation protocols. A realtime clock may be provided as part of the circuit.

The electrical stimulator current may pass between the selectedelectrodes and the reference electrode(s). A pulse duration timer mayprovide timing input PDC as determined by the CPU to the pulseamplitude/duration controller to control the duration of eachstimulation pulse. Likewise, the CPU may provide a pulse amplitudecontrol signal to the circuit by way of the serial peripheral interfaceto control the amplitude of each stimulation pulse.

Each output channel E1-E2 may include independent electrical chargestorage such as a capacitor SC that is charged to the high voltage VHthrough a respective current limiting diode CD. To generate astimulation pulse, the microcontroller output circuit 102 may providechannel select input data to switch component, as to the particularchannel E1-E2 on which the pulse may be passed. Switch SW may close theselected switch SW1-SW2 accordingly. The microcontroller may alsoprovide a pulse amplitude control signal PAC into a voltage-controlledcurrent source VCCS. As such, the pulse amplitude control signal PAC maycontrol the magnitude of the current I, and the circuit VCCS may ensurethat the current I is constant at that select level as dictated by thepulse amplitude control input PAC. For stimulation of human muscle, thecurrent I may be within an approximate range of 1 mA-20 mA. However, thepresent teachings are not limited to such range. Any appropriate rangemay be used with the present teachings.

Upon completion of the cathodic phase Qc as controlled by the pulseduration control signal PDC, the discharged capacitor SC may rechargeupon opening of the formerly closed one of the switches SW1-SW2. Theflow of recharging current to the capacitor SC may result in a reversecurrent flow between the relevant electrode 50 and the referenceelectrode 52, thus defining an anodic pulse phase Qa. The currentamplitude in the anodic pulse phase Qa is limited, preferably to 0.5 mA,by the current limiting diodes CD. Of course, the duration of the anodicphase may be determined by the charging time of the capacitor SC, andcurrent flow may be blocked upon the capacitor becoming fully charged.It should be recognized that the interval between successive pulses orpulse frequency PF may be controlled by the CPU 62 directly throughoutput of the channel select, pulse amplitude, and pulse durationcontrol signals as described at a desired frequency PF.

Some embodiments may implement from 1 to 8 or more independentpreprogrammed patterns. For each pattern, a stimulation session S may bepre-programmed into the stimulator circuit by a clinician through use ofthe input device. Each session S may have a maximum session duration ofapproximately 24 hours, and a session starting delay D. However, itshould be understood that these parameters are merely exemplary and notexhaustive or exclusive.

With continuing reference to FIG. 3 , a stimulus pulse train T mayinclude a plurality of successive stimulus pulses P. A stimulus pulse Pmay be current-regulated. It may also be biphasic, i.e., comprises acathodic charge phase Qc and an anodic charge-phase Qa. Alternatively,the stimulus pulse may be monophasic, i.e., comprises only a cathodiccharge phase or anodic charge phase, or contain more than 2 phases. Themagnitude of the cathodic charge phase(s) Qc, may be equal to themagnitude of the anodic charge phase(s) Qa. The current-regulated,biphasic pulses P may provide for consistent muscle recruitment alongwith minimal tissue damage and electrode corrosion. Alternatively or inaddition to, a stimulus pulse may be regulated by other parameters(e.g., voltage-regulated, charge-regulated).

Each pulse P may be defined by an adjustable current I (or voltage forvoltage-regulated, or charge for charge-regulated, etc.) and anadjustable pulse duration PD. The pulse frequency PF may also beadjustable. Further, the current I, pulse duration PD, and pulsefrequency PF may be independently adjustable for each stimulationchannel E. The amplitude of the anodic charge phase Qa may be fixed, butmay be adjusted if desired.

Pulse “ramping” may be used at the beginning and/or end of eachstimulation pulse train T to generate smooth muscle contraction, butother methods may be used as well. Ramping is defined herein as thegradual change in cathodic pulse charge magnitude by varying at leastone of the current I and pulse duration PD. In FIG. 3 , an embodiment ofa ramping configuration is illustrated in greater detail. As mentioned,each of the plurality of stimulation leads/electrodes 40, 50 may beconnected to the pulse generator circuit 60 via a stimulation pulsechannel E. As illustrated in FIG. 3 , two stimulation pulse channels E1and E2 may be provided to independently drive up to two electrodes 50.Stimulation pulse trains transmitted on each channel E1 and E2 may betransmitted within or in accordance with a stimulation pulse trainenvelope B1-B2, respectively. The characteristics of each envelope B1-B2may be independently adjustable by a clinician for each channel E1-E2.Referring particularly to the envelope B2 for the channel E2, eachenvelope B1-B2 may be defined by a delay or “off” phase PD0 where nopulses are delivered to the electrode connected to the subject channel,i.e., the pulses have a pulse duration PD of 0. Thereafter, according tothe parameters programmed into the circuit 60, the pulse duration PD ofeach pulse P is increased or “ramped-up” over time during a “ramp-up”phase PD1 from a minimum value (e.g., 5 μsec) to a programmed maximumvalue. In a pulse duration “hold” phase PD2, the pulse duration PDremains constant at the maximum programmed value. Finally, during apulse duration “ramp-down” phase PD3, the pulse duration PD of eachpulse P may be decreased over time to lessen the charge delivered to theelectrode 50. Further, it is possible to “ramp-up” and “ramp-down” forzero seconds, which indicates that there is no ramping.

This “ramping-up” and “ramping-down” is illustrated even further withreference to the stimulation pulse train T which is provided incorrespondence with the envelope B2 of the channel E2. In accordancewith the envelope B2, the pulse P of the pulse train T first maygradually increase in pulse duration PD, then may maintain the maximumpulse duration PD for a select duration, and finally may graduallydecrease in pulse duration PD.

As mentioned, the current I, pulse duration PD, pulse frequency PF, andenvelope B1-B2 may be adjustable for every stimulation channel E,independently of the other channel. The waveform shape (e.g.,rectangular, exponential, ramp; pre-pulse, post-pulse) and channelsynchrony (i.e., when stimulation through each channel starts and stopswith respect to the other channels) may also be adjustable. Thestimulation pulse generator circuit 60 may be pre-programmed with one ormore stimulation patterns, which may allow a patient to select theprescribed one of the patterns as required or otherwise desired duringtherapy. The pulse train, however, does not have to be constant (e.g.,frequency may vary). Additionally, the ramping parameters may beadjusted (e.g., off time, ramp up time, ramp down time, and hold time).

In some embodiments, the pulse generator 10 may include at least twostimulation pulse channels E. The stimulation pulse trains T of eachchannel E may be sequentially or substantially simultaneouslytransmitted to their respective electrodes 50. The pulse frequency PFmay be adjustable within the range of approximately 1 Hz toapproximately 100 Hz; the cathodic amplitude PA may be preferablyadjustable within the range of approximately 0.1 mA to approximately 40mA; and, the pulse duration PD may be preferably adjustable in the rangeof approximately 1 μsec to approximately 500 μsec delivered by thecircuit 60.

In alternative embodiments, the pulse generator may be implantable intoa patient's body and would generate stimulation in a similar fashion asdescribed previously for an external stimulator. In such embodiments,the pulse generator may be implanted in any appropriate location of apatient's body, including, without limitation, within the back, legs,torso and the like. With an implantable pulse generator, both thegenerator and the electrodes (and leads, if applicable) are underneaththe skin. As a result, a programmer may communicate with the stimulatorthrough the skin. Prior to placing the implantable pulse generator, apatient may use a percutaneous system as a trial.

According to one method of treatment according to the present teachings,percutaneous leads may be placed in the erector spinae muscles (see FIG.4 ), although this approach may be generalized to any muscle in theback, including, but not limited to, longissimus, iliocostalis,spinalis, multifidus, latissimus dorsi, rhomboid, serratus posterior,oblique external, oblique internal, quadratus lumborum, psoas major,psoas minor, trapezius, levator scapulae, splenius capitis, spleniuscervicis, semispinalis muscles, rotatores muscles, rectus capitisposterior muscles, interspinales, levatores costarum, obliquus capitisinferior muscle, obliquus capitis superior, rectus capitus posteriormajor, and rectus capitus posterior minor, and the leads may be placedin any tissue. First, the most painful regions on each side of apatient's back may be determined through patient-drawn diagrams of pain,verbal description of location of pain, manual evaluation, and/or othermethods. Specifically, a clinician may use his/her fingers to gentlypalpate the back, starting within the regions indicated on a paindiagram previously completed by the patient, and the patient mayindicate where pain is greatest on both the left and/or right sides.Once the most painful regions are located, the skin on these regions maybe prepared with antiseptic. On one or both sides of the back at themost painful regions, a sterile needle electrode (i.e., test needle) maybe inserted into the erector spinae muscles and connected to an externalpulse generator to deliver electrical stimulation (see FIGS. 5, 7A-7J).Alternatively, the electrode may not be connected to a pulse generator(e.g., the generator may be integrated or pre-connected with theelectrode (Bion®) or it may be radio frequency or otherwise wirelesslypowered). The electrode may be placed at the same spinal level (e.g.,L3, S1) as the most painful areas but a fixed distance (e.g., 2.5 cm)from the body's midline. Yet another approach may be to insert theneedle at an angle at a different site (on the dorsal/posterior,lateral, or ventral/anterior part of the body), so that the tip of theneedle may be positioned within the muscles directly beneath the site ofthe greatest pain (see FIG. 5 ). Needle insertion may be guided byultrasound, fluoroscopy, or any other appropriate method. The depth ofthe needle insertion may be guided by MRI scans or electromyography orby other known procedures for insertion of needles or the like into theback (e.g., paravertebral injections).

Intensity of the electrical stimulation provided by the pulse generatormay be increased on each side or on a single side to reach comfortablemuscle contraction (e.g., evaluated visually by movement of muscle,needle motion or utilizing an imaging modality such as ultrasound,thermal, infrared, MRI/PET, or biophotonics, by manual palpation, bynon-human palpation, by electromyography, by computer-aidedvisualization, by changes in electrical conductivity of tissue or bypatient report of muscle contractions). Alternatively, musclecontractions may be generated but may not be able to be observed by thesame means. For example, patients may describe experiencing sensationsthat are associated with muscle contractions, including, but not limitedto, tapping, tightening, pinching, pricking, or massaging. Oncecontractions have been evoked, the location of the needle insertion maybe marked, the needle removed, and the positioning of the needle (e.g.,depth beneath skin, angle with respect to surface of the skin) may bemeasured. In other embodiments, stimulation may proceed withoutconfirmation of muscle contractions. For example, a clinician may use astrong intensity likely to cause muscle contractions, but the clinicianmay choose not to verify that muscles have contracted.

As shown in FIG. 6 , percutaneous leads may be placed through entrypoints on a patient. An introducer may be used at the site or sitesidentified with the needle electrodes and may be placed at the depthidentified previously and using the needle positioning identifiedpreviously or the method may be completed without a test needle.Electrode placement may be guided by a predetermined map of muscleresponse generated by stimulation at different coordinates, where thecoordinates may be based on relative or absolute distances fromanatomical landmarks. This predetermined map may be individualized foreach patient or may be generalized for use across specific groups ofpatients (e.g., obese patients, tall patients, geriatric patients) orall patients. The patient may be given lidocaine along the anticipatedpathway of the percutaneous lead if he or she desires. The leads may beinserted and connected to an external pulse generator of any appropriateconfiguration. Stimulation may be delivered through the leads to verifyproper placement (e.g., stimulation-evoked muscle contractions). Theintroducers may be removed, leaving the leads within the target tissues.Following placement, the proximal portion of the lead, which may resideoutside of the patient's body, may be secured to the skin and coveredwith a waterproof bandage. Prior to leaving the clinic, a patient may beinstructed on the proper care of the lead exit sites. Patients may beinspected afterwards (e.g., within 48 hours) for analysis of the leadsand exit sites. The leads may be allowed to stabilize for one weekbefore the treatment period begins.

The lead may need to be repositioned to generate comfortable musclecontractions in a different part of the back, and this may be achievedbased on known innervation patterns for the paraspinal muscles or anyother appropriate muscle or muscle group. For example, because themedial, intermediate, and lateral branches of the dorsal ramus innervatelumbar paraspinal muscles positioned in the same medial-lateral order(i.e., multifidus, longissimus, iliocostalis) (FIG. 4 ), the lead may berepositioned medially or laterally to generate more medial or lateralmuscle activation, respectively (FIGS. 7A-E). Similarly, because theparaspinal muscles are segmentally innervated, the lead may berepositioned more superior or inferior to generate more superior orinferior muscle activation, respectively (FIGS. 7F-H). The depth of thelead may also generate different regions of muscle activation due to thebranching patterns of the dorsal ramus (FIGS. 7C, 7I, and 7J).

The approach according to the present invention, using one or morepercutaneous leads placed in tissue to cause muscle contraction, mayavoid cutaneous discomfort since stimulation is delivered away fromcutaneous receptors and closer to target peripheral motor neurons. Whileactivation of motor axons causes muscle activation, it may not beexpected to cause discomfort. The branches of the dorsal ramiinnervating the paraspinal muscles contain not only motor axons, butalso sensory axons. Motor axons typically have a larger diameter thanthe sensory axons that transmit the signals that lead to the perceptionof pain. The strength (i.e., intensity) of electrical stimulationrequired to activate axons increases as axon diameter decreases. Thus,motor axons should be activated at lower stimulation intensities thansensory axons, enabling comfortable activation of motor axons withoutactivation of painful sensory axons. Further, because of the placementof the leads subcutaneously within tissue, electrical stimulation may bedelivered far from cutaneous receptors and may avoid the painfulsensations generated during other methods, such as TENS.

Stimulation frequency and amplitude of the stimulation applied may bevariable, but in some embodiments may be fixed. Intensity may bemodulated by varying the pulse duration. Stimulation intensity may beset to generate strong, comfortable muscle contractions. As shown inFIG. 8 , each of the two percutaneous leads may be wrapped around apatient's respective side and connected to a pulse generator, such as abody-worn external pulse generators located on the front or side of theabdomen. In other embodiments, the external pulse generator may beplaced on any appropriate location, including, without limitation on theback, legs, or arms. Over the treatment period, such as three weeks, apatient may self-administer stimulation every day for a daily treatmenttime, such as a total of six hours/day (e.g., either two 3-hoursessions, or one 6-hour session). Patients may be able to partake intheir normal routines during stimulation. A patient may use the systemin any bodily position (e.g., while sitting, standing or laying down(supine, prone, or laying down on one's side)). The stimulator maymaintain an electronic log for compliance monitoring. In otherembodiments, stimulation may be administered under the guidance of aclinician (e.g., in an office, or clinic). At the end of the treatmentperiod, the leads may be removed in any appropriate manner, such as byapplying gentle traction.

Use of systems and methods according to the present teachings may beexpected to generate comfortable targeted activation of back musclesanywhere there is pain, including, without limitation the lumbar,thoracic, cervical and sacral levels. Percutaneous electricalstimulation may be expected to generate comfortable targeted activationof muscles that overlap the region of greatest pain. The activation ofback muscles may also be generated near, but outside of the region ofpain. The location of the target back muscles may be unrelated to theregion of pain and may be selected based on other criteria (e.g.,patient age, weight, height, medical history) or may be the same for allpatients. The pain may be acute, subacute, or chronic back pain. If thestimulation is used to treat acute or subacute pain, it may be used toprevent chronic pain in the future.

Contraction of muscles may be evoked using electrical stimulation inmany ways. Electrical stimulation may be used to activate motor axonsthat innervate the muscle and cause activation and contraction of themuscle. Stimulation may also be used to stimulate motor points ofmuscles, where motor axons enter a muscle. Stimulation may also be usedto activate the muscle directly without activation of the motor axons.However, threshold stimulation intensities for activation of motor axonsmay typically be lower than that of direct activation of muscle.Electrical stimulation may also be used to stimulate other parts of thebody to cause a reflex response that activates the target muscle.Stimulation may also be used to activate muscle by stimulation of thedorsal root of spinal nerve, ventral root of spinal nerve, dorsal rootganglion, spinal nerve, and/or the spinal cord. Stimulation may also beused to activate a structure that is not in the back (e.g., abdominalmuscle, shoulder muscle) that causes passive movement (e.g., stretching,compression, torsion) of a back muscle.

During the treatment period (e.g., three weeks) the treatment may reducepain while stimulation is on, and may lead to reduced pain whilestimulation is off. The muscle contraction is thought to provide painrelief that may also persist after the treatment period (carryovereffect) for several minutes to several months. Thus, this temporary(e.g., three weeks) treatment may provide long-term pain relief at leastas long as the treatment period itself (e.g., three weeks to one year).Further, this treatment may cause change to the nervous system thatrelieves pain.

Compared to individuals with healthy backs, patients with chronic backpain have reduced function, health-related quality of life, and range ofmotion. When treatments reduce chronic back pain, function,health-related quality of life, and range of motion improve. As aresult, the reductions in chronic back pain generated by the inventionmay be expected to result in improvements in function and significantimprovements in health-related quality of life and range of motion. Whencombined with other back pain therapies, may enhance overalleffectiveness.

Although the embodiments of the present invention have been illustratedin the accompanying drawings and described in the foregoing detaileddescription, it is to be understood that the present invention is not tobe limited to just the embodiments disclosed, but that the inventiondescribed herein is capable of numerous rearrangements, modificationsand substitutions without departing from the scope of the claimshereafter. The claims as follows are intended to include allmodifications and alterations insofar as they come within the scope ofthe claims or the equivalent thereof.

The invention claimed is:
 1. A system comprising: a helically or spirally formed lead configured to be percutaneously inserted into tissue of an animal body, the lead comprising an insulated and a de-insulated portion: a single electrode wherein the single electrode is formed from the de-insulated portion; and an external pulse generator operatively coupled with the lead, the external pulse generator applies an intensity of electrical stimulation through the single electrode, wherein the electrical stimulation is configured to activate motor axons of at least one muscle in a back of the animal body with back pain causing muscle contraction of the at least one muscle relieving the back pain of the animal body and wherein the electrical stimulation is configured to prevent activation of painful sensory axons.
 2. The system of claim 1, wherein the external pulse generator is configured to apply a first set of electrical stimulation parameters.
 3. The system of claim 2, wherein the external pulse generator is configured to apply a second set of electrical stimulation parameters, wherein the second set of electrical stimulation parameters are different from the first set of electrical stimulation parameters.
 4. The system of claim 3, wherein the first and second set of electrical stimulation parameters are selected from a group consisting of: frequency, pulse duration, amplitude, duty cycle, pattern of stimulus pulses, polarity, number of phases, and waveform shape.
 5. The system of claim 1, further comprising a second electrode operatively coupled with the external pulse generator.
 6. The system of claim 1, wherein the lead comprises a 7-strand stainless steel wire.
 7. The system of claim 1, wherein the insulated portion of the lead is insulated with a biocompatible polymer.
 8. An electrical stimulation device comprising: a lead adapted for percutaneous insertion within an animal body consisting of an open-coiled wire member, with a layer of insulation partially covering the open-coiled wire member and a de-insulated portion forming an electrode; and an external pulse generator operatively coupled with the lead, wherein the pulse generator delivers an intensity of electrical stimulation through the electrode, wherein the electrical stimulation is configured to activate motor axons of at least one muscle in a back of the animal body causing muscle contraction of the at least one muscle for pain relief and wherein the electrical stimulation is configured to prevent activating painful sensory axons.
 9. The electrical stimulation device of claim 8, wherein the electrode is wirelessly coupled to the external pulse generator.
 10. The electrical stimulation device of claim 8, wherein the lead is hardwired to the pulse generator.
 11. An electrical stimulation device comprising: a lead adapted for percutaneous insertion below skin of an animal body with back pain consisting of a multi-strand wire member formed into a helix from a plurality of stainless steel strands, with a layer of insulation partially covering an exterior of the lead; an electrode formed from a de-insulated portion of the lead; and an external pulse generator operatively coupled with the lead, wherein the external pulse generator delivers an intensity of electrical stimulation though the electrode for a prescribed period of time wherein the electrical stimulation is configured to activate motor axons of at least one muscle in a back of the animal body causing muscle contraction of the at least one muscle to relive pain and wherein the electrical stimulation is configured to prevent activation of painful sensory axons.
 12. The electrical stimulation device of claim 11, wherein the activation of the motor axons of the at least one muscle is generated by direct stimulation of at least one nerve innervating the at least one muscle.
 13. The electrical stimulation device of claim 11, wherein the electrode is hardwired through the lead to the pulse generator.
 14. The electrical stimulation device of claim 11, wherein the external pulse generator comprises a housing that includes a clip.
 15. The electrical stimulation device of claim 11, wherein the external pulse generator comprises a visual display.
 16. The electrical stimulation device of claim 11, wherein the external pulse generator comprises a data input device.
 17. The electrical stimulation device of claim 16, wherein the data input device comprises an increment switch, a decrement switch and a select switch.
 18. The electrical stimulation device of claim 11, wherein the intensity of electrical stimulation comprises a current within a range of 1 mA to 20 mA.
 19. The electrical stimulation device of claim 11, wherein the intensity of electrical stimulation comprises a pulse frequency of 1 Hz to 100 Hz. 